1. Field of the Invention
The present invention relates to waveguide polarization beam splitters, and particularly, pertains to a wire-grid polarization beam splitter including a planar or ridged waveguide, which is adapted to either transmit or reflect light within the waveguide in dependence upon incident polarization.
Furthermore, the present invention also relates to a novel method of fabricating a waveguide polarization beam splitter, and particularly a wire-grid polarization beam splitter with a planar or a ridge waveguide, which is adapted to be utilized in order to either transmit or reflect light within the waveguide in dependence upon incident polarization.
In essence, a waveguide polarization beam splitter comprises a key element in a photonic integrated circuit, whereby beam splitters of that type can be advantageously employed as directional couplers, as well as being useful as directional modulators and switches when utilized in conjunction with a polarization rotational waveguide element.
Nevertheless, it is conceivable that problems may be encountered in connection with the redirecting of light within a waveguide, for instance, such as at an angle of 90 degrees relative to the direction of initial propagation of the light upon use thereof with a polarization-rotating element, as may be currently known in the technology.
In view of the above-mentioned problem, which is prevalent in the present-state of the technology, various investigations have been conducted and attempts made in addressing the issue of redirecting light in different directions, the latter of which are at sharp angles relative to the original direction of propagation of the light within a waveguide. Ordinarily, this redirecting of the propagated light has been implemented through the utilization of cylindrical waveguides, for example, such as in the form of optical fibers, or through the intermediary of ridged waveguides, which, however, are subject to being burdened with large losses of light, thereby resulting in poor and consequently unsatisfactory degrees of efficiencies when the radii of curvature in redirecting the lights are reduced so as to be extremely small in size. Consequently, these light losses are generally ascribed as being due to so called a micro-bending phenomenon.
2. Discussion of the Prior Art
Heretofore, this particular aspect in the problems of encountered light losses has not been fully addressed in the technology, and any practical attempt in solving this problem in the redirection of the propagated light has ordinarily be in the employment of a directional coupler. However, directional couplers are primarily passive devices and enable only a fraction of the incident light to be redirected, whereby the redirected light is again bounded by relatively large radii of curvatures, which are necessitated due to the limitations resulting from micro-bending losses. Although attempts have been made at switching all of the light successfully into one arm of a directional coupler, such as by means of LiNbO3 and other kinds of electro-optical waveguide elements, the deviation of the light from the original direction thereof is, however, again limited in scope. Furthermore, although various types of wire-grid polarization beam splitters have been developed in the technology, none are designed to be operative within a waveguide and, consequently, are of essentially limited value within the context of the subject matter of the present invention.